A pressure sensor manufactured according to the MEMS (Micro Electro Mechanical Systems) technique is employed for a pressure sensor or a pressure switch provided on an industrial machine or the like, for example.
Such a pressure sensor includes a diaphragm formed by partially thinly working a substrate as a pressure sensing portion, for example, and detects stress or displacement caused when the diaphragm is deformed by receiving pressure.
A pressure sensor formed by bonding two substrates to each other is known as such a pressure sensor, for example (refer to Patent Document 1, for example).
In order to manufacture the pressure sensor described in Patent Document 1, a LOCOS oxide film is first formed on a surface of a first substrate to surround a prescribed region, and a second substrate is bonded to a surface of the LOCOS oxide film. Thus, a space is formed between the two substrates in the prescribed region. Then, a surface of the first substrate opposite to a surface provided with the LOCOS oxide film is cut/polished until the LOCOS oxide film is exposed. As a result, a remaining portion of the first substrate surrounded by the LOCOS oxide film forms a diaphragm.
A piezoresistance pressure sensor is obtained by forming a piezoresistor on the diaphragm. A capacitance pressure sensor is obtained by forming electrodes on both of the first substrate (a diaphragm portion) and the second substrate (a portion opposed to the diaphragm portion).